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Production of high levels of 8:0 and 10:0 fatty acids in transgenic canola by overexpression of Ch FatB2 , a thioesterase cDNA from Cuphea hookeriana
Author(s) -
Dehesh Katayoon,
Jones Aubrey,
Knutzon Deborah S.,
Voelker Toni A.
Publication year - 1996
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.1996.09020167.x
Subject(s) - thioesterase , canola , complementary dna , brassica , biochemistry , biology , transgene , substrate (aquarium) , chemistry , food science , botany , enzyme , biosynthesis , gene , ecology
The Mexican shrub Cuphea hookeriana accumulates up to 75% caprylate (8:0) and caprate (10:0) in its seed oil. An acyl‐ACP thioesterase cDNA from C. hookeriana , designated Ch FatB2 , has been identified, which, when expressed in Escherichia coli , provides thioesterase activity specific for 8:0‐ and 10:0‐ACP substrates. Expression of this clone in seeds of transgenic canola, an oilseed crop that normally does not accumulate any 8:0 and 10:0, resulted in a dramatic increase in the levels of these two fatty acids accompanied by a preferential decrease in the levels of linoleate (18:2) and linolenate (18:3). The Ch FatB2 differs from Ch FatB1 , another Cuphea hookeriana thioesterase reported recently, in both substrate specificity and expression pattern. The Ch FatB1 has a broad substrate specificity with strong preference for 16:0‐ACP and is expressed throughout the plant; whereas Ch FatB2 is specific for 8:0/10:0‐ACP and its expression is confined to the seed. It is proposed that the amplified expression of Ch FatB2 in the embryo provides the hydrolytic enzyme specificity determining the fatty acyl composition of Cuphea hookeriana seed oil.